This invention relates generally to road surface patching apparatus, and more particularly pertains to mobile equipment for use in applying filler in pavement cracks or joints, and to make pothole repairs.
The maintenance of hard paved road surfaces typically requires patching by filling of holes, cracks or fissures which develop from heavy use and/or climatic conditions. Moreover, the strip of filler normally applied between sections of new pavement tends to erode and/or deteriorate over time whereby replacement or patching is required.
Molten asphalt cement is typically used as a filler for such patching, and the art has recognized the value of intermixing reinforcing materials in the asphalt to increase the durability, thermal stability, and tensile strength of the patched area. One method of pothole patching in current use utilizes apparatus for blowing a pre-mixed aggregate and asphalt emulsion into a pothole to thereby form a patch. Another current method of crack or joint repair requires mixing of small-diameter, short-length polyester filament segments into a reservoir of preheated liquid bituminous patching material which is then dispersed through a hose to a manually-guided dispensing nozzle used to apply the material in a crevice or other area to be filled.
There are distinct advantages in the utilization of fiber-reinforced asphalt cement in road surface repair. The adherence characteristics of the asphalt cement are well-known. Equally well-known are the disadvantages inherent in asphalt cement as a patching material, such as its tendency to shrink and crack and its relatively low tensile strength. The addition of chopped fibers to reinforce the asphalt significantly increases its tensile strength, enhances its thermal stability, and provides a relatively durable and long-lasting repair.
A conventional crack or joint patching method employs apparatus having a heated vat or reservoir wherein bags of chopped fiber are dumped into the molten material to create the mix. The flowable mix is then pumped out through a large-diameter hose to a manually-held and directed wand or dispensing nozzle by means of which the material is pumped into the crevice or hole to be patched. There are a number of problems associated with this practice, including difficulty in obtaining uniform distribution of the fibers in the molten asphalt, accurately controlling the ratio of fiber fill to asphalt, and maintenance of the dispersal components of the apparatus which are required to pump and deliver a mixture of relatively high viscosity.
A major limitation of presently available equipment which combines reinforcing fiber with asphalt-type patching medium is the inability of the operator to vary the proportions of the combined materials in accordance with conditions or requirements of the area to be repaired.